Biocontrol of weeds in native ecosystems. Quentin Paynter

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1 Biocontrol of weeds in native ecosystems Quentin Paynter

2 Invasive plants in NZ Since 1769, >25,000 exotic plant spp. introduced (90% deliberately) from all over the world Naturalized seed plant spp. (2200) already outnumber native spp. (1900) & number is growing 328 spp. listed as environmental weeds in DOC consolidated list Europe North & South America Australia Asia Africa Other

3 The Cost Pastoral weeds cost ~$1.1 billion/yr (2005). Ecosystem service losses ~$2.52 billion/yr (2008). DOC & regional councils spend ~$18m/yr to reduce biodiversity losses from weeds but are failing to contain many weed populations. $ $ $

4 Weed Biocontrol in NZ Eradication of naturalised weeds rarely feasible: need to minimise harmful impacts Herbicides &/or mechanical control often not cost-effective or unsustainable in sensitive native ecosystems Landcare Research is the lead provider of classical weed biocontrol in NZ we end up with the weeds that are too intractable to be controlled by other means! Rejmánek, M & Pitcairn, MJ When is eradication of exotic pest plants a realistic goal. Turning the tide: the eradication of invasive species, Data: California Dept. Food & Ag.

5 What is Biological Control? A technique used worldwide where we attempt to restore the balance between a weed & the environment by reuniting it with some of its key natural enemies.

6 Isn t biocontrol risky?

7 Weed biocontrol safety record Stringent host-range testing required to demonstrate weed biocontrol agents are adequately host-specific to gain EPA approval for release in NZ Testing highly reliable e.g. nochoice starvation test (where an agent is confined on a test plant & either feeds or starves to death) is virtually infallible!

8 Weed biocontrol safety record NZ: ~90 yr history & no significant non-target attack on native or economically important exotic plants 1,2 Worldwide: 512 weed biocontrol agents released only 4 (0.8%) have serious non-target impacts: all on plants & in same genus as the target weed & all predictable (lower standards of biosafety in past their release would not be allowed today 3 ) Host-range testing has been improved to reduce potential risks still further. Potential benefits exceed risks 1,2 1 Paynter et al NZ Plant Prot Fowler et al J. Appl. Ecol Suckling DM & Sforza, RFH PloS one, 9, e84847

9 Biocontrol Pros & cons Selective & no health risks Sustainable: after initial investment, can provide long-term control at no cost Agents disperse naturally to control inaccessible weed infestations BUT no guarantees of success & slow vs instant results of herbicide Not all weeds suitable targets (e.g. kiwifruit) Weeds never eliminated totally

10 Density A successful biocontrol programme should progress like this: Weed Agent Damage threshold Release of bioagent Time 1.3

11 Success rate ~ 1 / 3 of programmes so successful other control options are no longer required; ~ 1 / 2 are partially successful (e.g. biocontrol effective in some habitats, but not in others) ~ 1 / 6 are failures (no impact) 1 We are working on improving success rate/cost-effectiveness! 1 Paynter et al J. Appl. Ecol, 49,

12 90 year history in NZ Early programmes targeted pasture weeds: 1 st major success St John s wort Hypericum perforatum in 1940s Recent NPV calculated for SJW beetle introduction is between $140m & $1,490 m (Benefit: cost ratios between 10:1 & 100:1) Benefits of SJW programme, have more than paid for all weed biocontrol programmes undertaken in NZ to date!

13 Ragwort Jacobaea vulgaris

14 Ragwort Economic evaluation of the impact of the ragwort flea beetle has begun. Current annual saving in herbicide use alone for the dairy industry estimated to be NZ$41m. Potential for this figure to be increased by a further $20m if the plume moth (released 2005) controls remaining ragwort stands.

15 Taking on Environmental weeds: Entyloma geratinae & mist flower Ageratina riparia 1 Mist flower declined by 98% & replaced by native plants 1 1 yr after 1998 release of white smut fungus Hebe acutiflora status changed from endangered to range restricted 3 yrs after fungus released 1 Barton et al. (2007) Biological Control, 40,

16 Heather Calluna vulgaris

17 Current Targets Alligator weed Banana passionfruit Boneseed Chilean needle grass Darwin s barberry Field horsetail Japanese honeysuckle Lagarosiphon Lantana Moth plant Old man's beard Pampas Privet Tradescantia Tutsan Wild ginger Woolly nightshade

18 Tradescantia Tradescantia fluminensis

19 In NZ, mats >200gm -2 (dry weight) prevent native forest regeneration NZ biomass gm -2 ; 83% samples > 200gm -2 Brazil biomass gm -2 ; 12% samples > 200gm -2 If difference is due to natural enemies in Brazil, then good prospects for biocontrol! Dense mat of Tradescantia in Waipu Gorge

20 Natural enemy surveys in Brazil Some work near Rio de Janeiro & São Paulo, but most surveys in uplands of Paraná, Santa Catarina & Rio Grande do Sul (good ecoclimatic match to NZ). Survey area 500 km

21 Tradescantia grows best on the slopes of the Brazilian Highlands plateau at altitudes between m

22 4 agents approved for release by EPA, expected to complement each other. Growing stems with leaves Dense mat of live stems without leaves Thin, short roots

23 Neolema ogloblini released 2011

24 Lema basicostata released 2012

25 Neolema abbreviata released 2012 Buckibrotica cinctipennis

26 Japanese Honeysuckle Lonicera japonica

27 Woolly Nightshade (Solanum mauritianum)

28 Chinese Privet (Ligustrum sinense)

29 Projects in development

30 Moth Plant (Araujia hortorum)

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32 Pampas (Cortaderia spp.)

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34 Wild Ginger (Hedychium spp.) Aborted apical growth

35 Information Sources Information on our website: The Biological Control of Weeds Book control-of-weeds-book Quarterly Newsletters wsletters/biological-control-of-weeds